<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    function ten(sum, num) {
      let arr = [1, 2, 3, 4, 5, 6, 7, 9, 10]

      for (let i = 0; i < arr.length; i++) {
        sum += arr[i]
      }
      return num - sum

    }
    console.log(ten(0, 55))
  </script>
</body>

</html>